1. Field of the Invention
This invention relates to a frequency or call-unit count device.
2. Description of the Related Art
This type of call-unit count device has heretofore been configured as a portable module such as an IC card having a memory circuit such as an Electrically Erasable Programmable Read Only Memory (hereinafter called EEPROM) or the like. When a command for adding a frequency or call unit (call-unit add command) is issued or given from a card reader, the call-unit count device adds the call unit given by the call-unit add command to call units (corresponding to the sum of call units which have been given up to now by the input call-unit add commands) stored in the EEPROM at this time, and stores the call units obtained by its addition therein.
Described specifically, the EEPROM is divided into a plurality of levels respectively composed of a plurality of bits. In this type of EEPROM, bits in the least significant level are set to "1" bit by bit each time a command for adding one frequency or call unit (hereinafter called "one call-unit add command") is given, for example. When all the bits in the least significant level are brought to "1", a bit in a level higher by one than the above level are brought to "1" and all the bits in the least significant level are set to "0" in response to a one call-unit add command given in the next place. Thus, the conventional call-unit count device performs a carry from a low-order level to a high-order level by inputting one call-unit add command after the transition of all the bits in the least significant level from a "0" state to a "1" state.